Treatment of wool to diminish shrinkage



Patented June 22, 1943 TREATMENT OF WOOL TO DIIVIINISH SHRINKAGE Henry Phillips and William Robert Middlebrook,

' Leeds, England No Drawing. Application April 20, 1939, Serial No. 268,988. In Great Britain April 21, 1938 -9 Claims. (01, 195-5)- This invention relates to a treatment of wool or wool materials, or materials containing wool, in the form of loose fibres or in a manufactured form such as yarn and fabric so that the wool has a lessened tendency to felt when washed in aqueous liquors.

In describing this invention the term felt is understood to refer to that property of wool which causes the individual fibres to interlock,

when washed in acid or alkaline liquors, so that 10 There is another cause of shrinkage in wool goods, namely the stretching of the wool fibres during spinning, weaving and knitting. When the goods are washed in alkaline liquor this stretch is relieved and the goods shrink; this phenomenon is known as relaxation shrinkage.

It is an object of this invention to treat the wool in such a manner that both kinds of shrinkage substantially disappear.

It is known that felting properties of wool and therefore the irreversible (felting) shrinkage may be diminished by treating the wool with a proteolytic enzyme, but the action of the enzyme proceeds only slowly.

The present invention consists in treating-wool or materials consisting of or containing wool with a solution of a vegetable protease, especially papain, in presence of a sufficient quantity of sodium bisulphite.

It appears that the sodium bisulphite acts by be supposed to exist in the keratin of the wool to thiol (-SH) groups and that the action of 3 the vegetable protease is thus selectively directed to certain parts of the structure of the wool,

which is thereby altered so that it becomes nonfelting without the loss of the protein material essential for its mechanical strength. The effect is certainly not simply one of activation of the protease, for it is not attained with quantities of sodium bisulphite such as are usual in the case 46 of activators. As will be evident from the examples given hereinafter, in the process of this invention the sodium bisulphite is used in an amount which is not less than about 38 times the quantity of papain. Moreover, the optimum result'is not obtained unless the papain solution contains at least 1 per cent of its weight of sodium bisulphite.

The conditions under which the woolmust be treated by'the process of the invention to reduce it to anyv desired degree its tendency to felt may be varied widely to suit the nature of the wool under treatment and the potency of the protease used. We have found generally that unless the wool loses about 1-3 per cent of its weight during. the treatment, its felting properties are not destroyed entirely. If the wool is required to be substantially non-felting, the conditions under which the wool is treated with any given protease must therefore be so chosen that about 1-3 per cent of the wool substance passes into solution.

To cause wool to suffer this loss in weight rapidly, we have found that not only should sodium bisulphite -be added to the solution of vegetable protease, for instance, papain; but that the process is preferably carried out at a suitable pH value.

We have found that the sodium bisulphite, after partial neutralization by alkali, will serve to maintain the hydrogen ion concentration in the near neighborhood of pH Gil at which the action of the solution on the wool is very rapid. Even under such conditions we have foundthat the activity of the solution towards wool can be still further increased by the addition of urea, or by the addition of cysteine, addedv either as such, or in the form of cystine, or cystine mixed with other amino-acids, as is obtained by the hydroly sis of wool-with aqueous hydrochloric acid.

We have found a solution of 1 part commercial papain in 4000'parts of water, activated by the addition of 40 parts of sodium bisulphite, and its pH value adjusted to 6.7 by the addition of the necessary amount of alkali as sodium carreducing dithio SS-) groups which may 35 bonate will make wool substantially non-felting most quickly when the temperature of the solution is maintained at C. The duration of treatment under these conditions is 10-60 minutes, being longer for fine wools than for coarse wools, and longer for compact fabrics of tightly twisted yarns than for loose fabrics of loosely twisted yarns. In all circumstances it is essential to limit the duration of treatment so that the wool suffers the minimum loss in weight consistent withthe desired degree of tendency not to felt. The duration of treatment can be curtailed if a more concentrated solution of the papa-in is used.

An advantage of the use of papain or the like activated by sodium bisulphite in water is that the solution has a bleaching action on the wool, and the bleach obtained is more permanent to the action of alkaline wash liquors than the bleach normally obtained by the action of a solution of sodium bisulphite on wool. A further advantage of the use .of papain or the like activate by sodium bisulphite in water is that Example 2 Wool yarn (100 parts) wound in cheese form or as prepared for cheese dyeing, is placed in a cheese dyer constructed of material resistant to solutions of sodium bisulphite, such as stainless steel. A solution containing 0.4 part of comrnercial papain in 1600 parts of water to which 16 parts of sodium bisulphite and sufficient sodium hydroxide-to bring its pH value to 6.7 has of stretch when washed in alkaline liquors. The

treatment thus removes at one and the same time v the two chief causes of shrinkage, namely, the irreversible shrinkage due to the felting of the wool fibres and the reversible shrinkage due to the release of tension in the stretched fibres.

When the stretched wool fibres of yarns and fabrics are prevented from contracting during treatment in a solution of papain activated by sodium bisulphite and also during subsequent rinsing and drying, they acquire a set which is more permanent to wasihng in alkaline liquors than is the temporary set imparted to wet yarns or fabrics by drying them in the stretched condition.

One objection sometimes raised against processes which make wool non-felting is that it is difficult to manufacture from the treated wool a fabric which has cover, 1. e.,.a soft surface produced by causing the fibres on the surface to felt. We have found that it is possible to produce by our process unshrinkable fabrics possessing cover by milling the fabric in a solution of papain activated by sodium bisulphite. We find that by such methods the surface fibres become suitably felted before the enzyme solution has acted for a sufficient length of time to inhibit felting. a

The process may be advantageously applied to wool materials containing cellulosic fibres such as cotton and rayon. These cellulosic fibres are substantiallyunchanged by treatment with solutions of papain containing sodium bisulphite.

When solutions of papain containing sodium bisulphite are used to treat wool materials containing scoured (de-gummed) silk, the silk is substantially unaffected. When solutions of papain containing sodium bisulphite are used to v treat wool materials containing raw silk, the layer of best surrounding the real and valuable fibroin filaments of the silk is attacked and is partially or wholly removed.

Wool, or wool material, or material containing wool that has been treated with proteases as described can be rinsed with water and then dried in any known or suitable manner.

The'following examples illustrate the invention. The parts .areby weight.

"Erample 1 wool is rinsed in running water and whizzed in a hydro-extractor to remove excess water.

been added is pumped through the cheeses, and.

heat is applied during about 12 minutes to raise the temperature of the-solution to 65. C. After the solution has circulated through the cheeses of wool yarn in the machine for minutes in all the solution of papain is run of! and water is then circulated through the cheeses so as to rinse the treated yarn.

Example 3 100 parts of scoured wool fabric is treated for minutes-at about 65 C. with a solution of 0.325 part of commercial papain in 1250 parts of water with the addition'of 12.5 parts of sodium bisulphite and 2.1 parts of sodium hydroxide. The pH of this solution is 6.7. The fabric is then rinsed in running water and dried in any known or suitable manner.

Example 4 100 parts of mixed fabric containing parts of wool are treated for 45 minutes at about C. with 0.325 part of commercial papain in 1250 parts of water to which 12.5 parts of commercial Egtample 5 100 parts of scoured wool fabric are milled for about 15 minutes at 65 C. in a solution of 0.325

part of commercial papain in 1250 parts of water with the addition of 12.5 parts of sodium bisulphite and 2.1 parts of sodium hydroxide tobring r the pH value of the solution to 6.7. The fabric is then rinsed in running water and dried in any known or suitable manner. It is to be understood that in the appended claims the term woo is used to include wool as loose fibres and also as manufactured goods such as yarns and fabrics;

also to include wool in blends of textile fibres and in manufactured goods containing other textile fibres.

Having thus described the nature of the said invention and the best means we know of carrying the same into practical effect, we claim:

1. A process for the treatment of wool for the purpose of diminishing shrinkage, wherein the wool is subjected to the action of a solution of papain containing sodium bisulphite in which the concentration of sodium bisulphite is at least 1 per cent and in which the weight of sodium bisulphite is at least 38 times the weight of papain.

2. A process as claimed in claim 1, wherein thesolution contains urea.

3. A process as claimed in claim 1, wherein the solution contains cysteine.

4. A process as claimed in claim 1, wherein the wool is maintained under tension sufiicient to prevent contraction while it is subjected to the action of the solution and to subsequent rinsing and drying.

5. A process as claimed in claim 1, wherein the wool in the form of a fabric is milled during its subjection to the action oi! the solution.

s. a process as claimed 13 claim 1, wherein the action of the solution is continued until the J 8. A process for the treatment of wool for the purpose oi diminishing shrinkage, wherein the wool is subjected to the action ot a solution of papain containing sodium bisulphite and having a pH value of about 6.7, in,which solution the concentration of sodium bisulphite is at least 1 per cent and in which the weight of sodium bisulphite is at least 38 times the weight of papain.

9. A process as claimed in claim 1, wherein the solution also contains a substance which gives rise to cysteine.

HENRY PHILLIPS. wnmm ROBERT MIDDLEBROOK. 

